1. Field of the Invention
This invention relates to a recording/reproducing apparatus for a magneto-optical disc employed as a recording medium for information signals. More particularly, it relates to a recording/reproducing apparatus for a magneto-optical disc in which the magneto-optical disc, disc rotating and driving means, an optical head, an external magnetic field generating means and control means are accommodated and unified in an outer casing.
2. Description of the Related Art
There has hitherto been proposed a magneto-optical disc recording/reproducing apparatus into which a disc cartridge having the magneto-optical disc housed rotatably therein is loaded with the disc loaded therein for recording and/or reproducing information signals on or from the magneto-optical disc.
The magneto-optical recording/reproducing apparatus includes a loading unit for loading the disc cartridge with the magneto-optical disc loaded therein, a disc rotating and driving unit for holding the magneto-optical disc housed within the disc cartridge loaded in position for rotating and driving the disc, an optical head device for recording information signals on the magneto-optical disc rotationally driven by the disc rotating and driving unit or for reproducing information signals recorded on or from the magneto-optical disc, and an external magnetic field generating device arranged oppositely to the optical head device with the magneto-optical disc in-between for applying a magnetic field in a direction perpendicular to the magneto-optical disc for recording information signals on the disc.
A loading unit for loading the disc cartridge includes a cartridge holder arranged for holding the disc cartridge inserted into the main body of the apparatus in a state parallel to the bottom of the main body. The cartridge holder is adapted for being moved vertically within the main body of the apparatus by a cam mechanism etc. The loading unit holds the disc cartridge maintained by the cartridge holder in a horizontal direction with respect to the main body which is the direction extending parallel to the major surface of the magneto-optical disc. When the disc cartridge is at a position in which the center of the magneto-optical disc placed within the disc cartridge is substantially coincident with the center of rotation of the disc rotating and driving unit, the loading unit causes the disc cartridge to be lowered towards the disc rotating and driving unit. With the disc cartridge thus being lowered, the magneto-optical disc placed within the disc cartridge may be held on the disc table of the disc rotating and driving unit.
The optical head device is arranged within the main body of the apparatus in a position facing a signal recording surface on the major surface of the magneto-optical disc rotated by the disc rotating and driving unit. The optical head device is supported for being moved radially across the inner and outer peripheries of the disc. The optical head device is moved along the radius of the magneto-optical disc rotationally driven by the disc rotating and driving unit for enabling the light beam to be radiated on substantially the overall region of the signal recording surface of the magneto-optical disc for recording and/or reproducing information signals on substantially the entire signal recording surface of the magneto-optical disc.
The optical disc also includes an object lens driving unit for causing the light beam radiated towards the magneto-optical disc to follow in-plane deviations or offsets caused by the disc rotation by way of performing focusing servo and tracking servo control operations. The object lens driving unit supports the object lens, adapted for converging the light beam on the signal recording surface of the magneto-optical disc, by means of a supporting member, such as a resilient plate spring, for movement in two directions, that is in a direction along the optical axis of the object lens and in a direction at right angles thereto. Besides, the object lens driving unit causes the object lens to be moved along the optical axis of the object lens and in the direction at right angles thereto by electro-magnetic driving means.
The electro-magnetic driving means driving and moving the object lens is made up of a driving coil mounted on a lens bobbin supported by a supporting member for holding the object lens so as to be supplied with a driving current based on focusing and tracking error signals for effecting focusing servo and tracking servo, and a magnetic circuit for moving the object lens along the optical axis and in a direction at right angles thereto when the current flows through the driving coil.
The external magnetic field generating device, provided within the main body of the apparatus with the magneto-optical disc in-between, is adapted to approach the disc when recording information signals thereon for applying a perpendicular magnetic field to the disc.
Meanwhile, in the magneto-optical disc recording and/or reproducing apparatus provided with a loading unit adapted for loading the magneto-optical disc housed within the disc cartridge on the disc rotating and driving unit after the disc cartridge introduced into the main body of the apparatus is moved horizontally and then vertically with respect to the main body of the apparatus, the loading unit becomes complicated in structure to render it extremely difficult to simplify the various devices or units provided in the main body to reduce the size of the apparatus, while the assembling operation is rendered troublesome.
Besides, since the optical head device of the magneto-optical recording/reproducing apparatus has a unitary structure comprised of an optical block inclusive of a light source radiating a light beam, an object lens for converging the light beam on the magneto-optical disc and an object lens driving device for driving and moving the object lens, the optical head device is increased in size and weight, resulting in increased sizes of a driving unit for moving the optical head device and means for supporting the optical head device.
Meanwhile, it may be contemplated to use a magneto-optical disc of smaller size to reduce the size of the magneto-optical disc recording and/or reproducing apparatus. Although the main body of the apparatus may be reduced in size by employing a small-sized magneto-optical disc, a sufficient recording capacity of the information signals and hence the practical utility of the magneto-optical recording and/or reproducing apparatus aimed at a larger storage capacity cannot be assured.